The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Positive temperature coefficient (PTC) thermistor, as a protection element in over-current or over-temperature condition, is widely used in computer and its peripheral equipment, mobile phone, battery pack, telecommunication equipment, network device, transformer, industrial control equipment, vehicle and other electronic products. For example, a barium titanate PTC thermistor is widely used in various industries because of its high temperature coefficient.
A traditional barium titanate PTC thermistor generally has a curie temperature of about 120 degree Celsius. Currently, in order to increase an operating temperature of the barium titanate PTC thermistor, there are many studies on semi-conduction process of barium titanate powder, for example, a donor doping or an acceptor doping may be carried out. The donor doping may be processed by using Pb, Sr, Ca, Y, Nb, Bi, Ce or La, and the acceptor doping may be processed by using Mn, Fe or Mg. However, those barium titanate PTC thermistors may have a high ambient resistance. Also, the sintering process during the semi-conduction process may be hard to control, thus the barium titanate powder may be unevenly semi-conducted. In this way, the barium titanate powders may be nonuniform, thus the barium titanate PTC thermistor may have a high grain resistance and a high grain boundary resistance. Therefore, the barium titanate PTC thermistor may have a high ambient resistance and a decreased lift-to-drag ratio, which greatly restrict its development and application.